Enhanced photoactivity of Cu-deposited titanate nanotubes for removal of bisphenol A

One-dimensional nanotubes are promising nanostructured materials for a wide variety of environmental applications. In this study, the Cu-deposited titanate nanotubes (TNTs) were fabricated using an alkaline hydrothermal method at 150°C and then 0.5-2wt% Cu(II) ions were photodeposited onto the calcined TNTs at 500°C for enhanced photodegradation of bisphenol A (BPA) under illumination of 365nm UV light. The as-synthesized TNTs showed tubular structures with the outer diameter and inter-layer spacing of 7-10 and 0.8nm, respectively. The X-ray absorption near-edge spectral results provided a strong support on the partially structural change from layered trititanate to anatase TiO₂ through the distortion of octahedral TiO₆ unit at 500°C and the production of mixture of CuO and Cu₂O after photodeposition of Cu ions, resulting in the formation of Cu-deposited TiO₂/TNT nanocomposites to enhance the photocatalytic activity. A nearly complete removal of BPA by the Cu-deposited TiO₂/TNTs was observed, and the pseudo-first-order rate constants (k_obs) for BPA photodegradation by Cu-deposited TiO₂/TNTs at pH 7.0 were 1.8-5.2 and 4.3-12.7 times higher than those of pure Degussa P25 and ST01 TiO₂, respectively. In addition, the k_obs for BPA photodegradation reached the maximum value of 0.253±0.032min^-1 at 1wt% Cu(II). The X-ray photoelectron spectra showed that the ratio of Cu₂O to total Cu increased from 3.2% in the dark to 35.2% after illumination of 365nm UV light for 5min. In addition, electron paramagnetic resonance results indicated that the copper ions could serve as the electron mediators to prolong the retention time of photo-generated radicals, resulting in the enhancement of photodegradation efficiency and rate of BPA by Cu-deposited TiO₂/TNTs.